Dimensional Stability of Extended-Storage Alginates

Objectives: The purpose of this investigation was to evaluate the dimensional accuracy over time of extended-storage irreversible hydrocolloids with purported dimensional stability for up to 100 hours. Methods: Impressions were made of stainless steel dies in accordance with ADA Specification 18 (1992) using three different alginates, two extended-storage (Alginmax, Kromopan) and one conventional (JeltratePlus). The impressions were stored for 30 minutes, 48 hours or 100 hours (N=5 impressions/material/storage time). Following the respective storage times, dimensional accuracy was measured by comparing the length of the middle horizontal line in the impression to the same line on the die and computing the percent difference. Results: A 2-factor ANOVA (α=0.05) indicated a significant interaction effect of material and storage time (p=0.018) and a significant main effect of material (p=0.004) on dimensional accuracy. All materials exhibited shrinkage after 30 minutes, with the conventional alginate continuing to shrink to -0.79% by 100 hours. In contrast, after initial 30-minute shrinkage, the extended storage alginates expanded, with Kromopan going from -0.77% at 30 min to -0.26% shrinkage after 100 hours and Alginmax from -0.20% at 30 min to -0.003% shrinkage after 100 hours. Conclusion: The evidence suggests that the extended-storage alginates were dimensionally stable after 100 hours and thus, delayed pouring should not adversely affect dimensional accuracy. Funded by UMKC SOD Rinehart Foundation.